1. Field of the Invention
The present invention is concerned with a carrier system for carrying electronic parts such as a silicon wafer, surface glass for an LCD, a photomask for an IC or the like in or out of a variety of processing devices and measuring devices within a clean room.
2. Prior Art
In the case of effecting various kinds of processes on, for instance, silicon wafers or measuring its performance by means of a measuring device, these operations are to be performed in a clean room which has to be shut off from the dust. The silicon wafers are in general accomodated in a shelf type cassette; and a carrier system for taking each individual wafer therefrom and carrying it onto a stage of the processing device or the like requires a means appropriated to the clean room in which infinitesimal drops of oil and metallic powder are not absolutely present.
As a conventional carrier system of this type, a belt conveyor type device has already been put into practical use. However, since such a device is incapable of moving vertically or laterally, a lifting/lowering device needs to be provided in the cassette accomodating the wafers. In addition, a process in which the wafers are taken in and out is confined to one direction, and the placement of the cassette and of the processing device is likewise limited, thereby unfavourably restricting an installation space in the clean room.
On the other hand, there has heretofore been proposed a method of carrying the silicon wafers with the help of a carriage. If a general linear way be adopted for the purpose of stably moving the carriage with high accuracy, the metallic powder and the infinitesimal drops of oil will be scattered from grooves provided with a multiplicity of rigid balls used for the linear way, which leads to such a problem that the clean room is degraded in cleanness.